1. Field of the Invention
The present invention relates to a curable polyvinyl ether composition created by using a novel catalyst system for the synthesis of polyethers from vinyl ether monomers or polymers. This catalyst system comprises a platinum complex catalyst and silicon hydride cocatalyst. The invention also relates to a method of producing polyethers from vinyl ether monomers or polymers using the above-mentioned catalyst system.
2. Technology Review
Platinum catalysts have long been known to promote the hydrosilation reaction. These platinum catalysts have been used in the production of epoxysilicone compositions and vinylsilicone compositions. See, for example, J. L. Speier, "Homogeneous Catalysis of Hydrosilation by Transition Metals", in Advances in Organometallic Chemistry, Vol. 17, pp. 407-447 (1979), F. G. A. Stone and R. West, eds., Academic Press (New York, San Francisco, London); Aylett, Organometallic Compounds, Vol.1, John Wiley, New York 1979, p. 107; and Crivello and Lee, "The Synthesis, Characterization, and Photoinitiated Cationic Polymerization of Silicon-Containing Epoxy Resins", J. Polymer Sci., Vol. 28, John Wiley, New York 1990, pp. 479-503. Generally, the hydrosilation catalysts used are complexes of platinum, palladium, rhodium, iridium, iron or cobalt. In particular, platinum-containing catalysts have been widely used for this purpose.
Platinum containing catalysts, such as the Ashby, Karstedt, Speier and Lamoreaux catalysts have been found highly useful as catalysts employed in the hydrosilation reaction, i.e. the addition of Si--H containing compounds to olefinic and acetylenic bonds (B. J. Aylett, Organometallic Compounds, Vol 1, John Wiley, New York, 1979, p. 107; J. L. Speier, Adv. in Org. Chem., Vol. 17, 407, 1974). This chemistry is extensively practiced at the General Electric Silicone Products Division for the synthesis of silicone intermediates and in the production of heat cured elastomers and coatings.
These platinum catalysts, however, until now have not been employed in the polymerization of vinyl ether monomers or polymers. Traditionally, vinyl ether monomers and polymers were polymerized under cationic polymerization conditions (C. E. Schildknecht, Vinyl and Related Polymers, John Wiley and Sons, 1952, p.593.). In our own work, we have employed onium salts for the thermal and photochemical cationic polymerization of vinyl ether monomers (J. V. Crivello, Adv. in Polym. Sci., 62, 1 1984). At the same time, vinyl ethers undergo free radical homopolymerization very sluggishly but copolymerize vigorously with monomers having electron deficient double bonds. There is, however, no mention in the literature of the polymerization of vinyl ether containing monomers and polymers in the presence of platinum containing catalysts.
The disadvantages of the traditional catalysts are that they tend to be required in larger quantities, to induce color and oxidative instability in the final cured resin, or corrode metals in contact with the resin. The present inventions use of platinum catalysts to promote vinyl ether polymerization provides numerous advantages over catalysts presently used to catalyze such polymerization. These advantages include the use of low levels of catalyst and the low tendency of catalyst residues to induce color and oxidative instability in the final cured resin, or corrosion of metals in contact with the resin. The novel polymerization catalysts tend to have excellent solubility in silicon-containing vinyl ether monomers, whereas other initiators, eg. onium salts, have very poor solubility.